The present invention relates generally to an information recording/reproducing apparatus for recording and reproducing information on and from a disc-like recording medium such as a magnetic disc and an optical disc, and more particularly to such an information recording/reproducing apparatus for verifying or confirming the quality of the information recorded on the disc-like recording medium.
Recently, in accordance with high-speed operation and high performance of computers there is also required high-speed operation and high performance of peripheral equipment. Particularly, it is strongly required for secondary storages such as a magnetic disc drive and an optical disc drive to reduce the access time concurrently with ensuring high reliability so as to increase the data transfer speed and the capacity. Thus, in practical use, in order to reduce the weight of the recording/reproducing head, to increase the rotational speed of the recording medium, to increase the recording density and to reduce the access time, the MCAV system (Modified Constant Angular Velocity system) for recording and reproducing is known where the rotational speed of the recording medium is made constant so as to change the frequency of the demodulation and modulation in accordance with the access position. This MCAV system is arranged such that the recording medium is radially divided from the inner circumference to the outer circumference into a plurality of groups each of which has a constant number of sectors, and in each of the groups one or more sectors are increased or decreased to perform the division into the groups so that the recording pits are formed constantly at the inner and outer circumferences thereof.
For writing data on the recording medium, in view of reliability, after completion of operation of the recording of data (which will be referred hereinafter to as writing), the data is read out so as to check the quality of the written data (which will be referred hereinafter to as verification), that is, a write-and-verify operation is performed after recording. This operation will be described hereinbelow with reference to FIG. 1 showing a general arrangement of an optical disc system. In FIG. 1, data outputted from a host computer 1 to be written- are inputted through a host interface 2 to a buffer memory 4 of a controller 3. In response to start of storing the data to the buffer memory 4, the data are supplied to an EDAC 5 in units of an amount corresponding to one sector of the recording medium where an error-correction code is added. The EDAC 5 acts as a bit error detection and correction circuit in which a predetermined bit is inserted into the data in accordance with an adequate calculation equation so as to find the error bit position when an error such as bit inversion occurs on reproduction. Thereafter, the data are supplied to a MODEM 6 for modulation to a code suitable for the recording on the optical disc and demodulation of the reproduced signal, and then supplied to a drive unit 7 to be written through a recording/reproducing head 8 on a recording medium 9. The MODEM 6 functions as a modulation and demoduation circuit to perform the modulation for recording to the recording medium 9 and perform the demodulation of the signal read out from the recording medium 9 to the original data before the recording.
Further, in the case of performing the write-and-verify operation, the data stored in the buffer memory 4 is kept as it is until the sector in which the data are recorded is completely verified, and when a problem is found by the verification, the data kept in the buffer memory 4 are transferred to the drive unit 7 for a changing process to other sectors.
FIG. 2 is an illustration of a process of a write-and-verify command corresponding to the number of the recording sectors where the vertical axis represents the time (rotational speed) and horizontal axis represents the number of the recording sectors. For example, in cases where the buffer memory 4 has a capacity corresponding to 48 sectors, the data to be stored in the recording medium 9 correspond to 56 sectors, and the overall 48 sector capacity is used for the write-and-verify operation, when the data corresponding to 48 sectors are transferred from the host computer 1, the data transfer is once interrupted and the data corresponding to 48 sectors stored in the buffer memory 4 are recorded on the recording medium 9 from a sector m (logic block address) up to a sector m+47. This procedure is indicated by a character A in FIG. 2.
Secondly, with the recording/reproducing head 8 seeking (moving the head) for the track of a sector m, preparation is made for the verification as indicated by B in FIG. 2. After a predetermined sector-waiting time as indicated by C in FIG. 2, that is, while the target sector m arrives, the data from the target sector m up to the sector m+47 are read out and transferred to the controller 3. This transferred data are verified in quality (bit error, read level and others) in units of one sector as indicated by D in FIG. 2. If there is no problem, the buffer memory 4 is released. On the other hand, if there is a problem, the data of the buffer memory 4 corresponding to the sector are supplied to the drive unit 7 so as to be recorded in a sector-changing area on the recording medium 9. Thereafter, the portion of the buffer memory 4 corresponding to the changed sector is released and the next data are transferred from the host computer 1 to this released portion.
When the verification is completed up to the sector m+47, under control of the controller 3, the recording/reproducing head 8 of the drive unit 7 seeks the next sector m+48, and the remaining data corresponding to 8 sectors are transferred through the EDAC 5 and the MODEM 6 to the drive unit 7. After waiting for a given write-sector as indicated by E, as well as described above, the writing operation F, seeking operation G, verify-sector waiting operation H and verification J are successively effected as illustrated in FIG. 2.
In such an information recording/reproducing apparatus, in the case that the write-and-verify operation is performed under the condition of division into a plurality of blocks, when the number of the sectors to be written and verified at a time in the blocks other than the final block is made constant, particularly in the MCAV system, the number of the sectors in one track is increased or decreased in each of the respective groups whereby the seeking operation B is effected between the writing operation A and the verification D, and the verify-sector waiting time C varies in each of the respective groups.
Accordingly, in accordance with variation of the executing speed in each of the groups, the operation becomes unstable when viewed from the host computer 1, and a problem arises in that the entire processing is delayed when the sector-waiting time becomes long. FIG. 3 shows a state wherein the data to be recorded are divided into a plurality of blocks and the number of the sectors in one track is 28 under the condition that the capacity of the buffer memory for the writing operation A and the verification is fixed to 48 sectors. Further, in FIG. 3, for writing data by 48 sectors from the sector m, the seeking operation is performed from the sector (m+47), taken after writing the data corresponding to one revolution (28 sectors) plus 20 sectors, to the sector m for the verification. During the seeking operation, a preparation for the verification is made. The time period for the seeking operation and the verification preparation is indicated by T in FIG. 3. Here, for example, in cases where about 8/28 of the time required for one revolution of the recording medium 9 is required as the time for the seeking operation and verification preparation, the first verified sector m is immediately detectable after the completion of the verification preparation and hence the sector-waiting time becomes at a minimum.
Further, FIG. 4 shows the case that the number of the sectors in one track is 26 under the condition that the buffer memory capacity for the writing operation A and the verification D is fixed to 48, and further shows a state that the first sector m for the verification is passed when the verification preparation (seeking operation) is effected after 48 sectors are written.
In comparison with the state illustrated in FIG. 3, in the case of the FIG. 4 state that the sector m is passed, the verification is performed after elapse of the time period corresponding to one revolution and hence the verification waiting time is lengthened by the time approximately corresponding to one revolution to cause the execution time to be delayed. The verification waiting time is always constant in the same group but the execution time is rapidly shortened or lengthened when the verification is effected over different groups, and hence the operation viewed from the host computer 1 becomes unstable and further the write-and-verify execution time becomes long because the sector-waiting time becomes long. Generally, the sector-waiting time is lengthened to decrease the execution speed in accordance with increase in the amount of the procedure (erase, recording, confirmation and others) in the write-and-verify operation and the amount of information to be recorded and further in accordance with decrease in the capacity of the buffer memory in the controller 3.